In recent years legislation has been enacted which requires that containers for certain products such as aspirin and other drugs have closures which are "child resistant", that is, which cannot easily be opened by a child by simply unscrewing a cap or pushing it off with the thumb. One type of child resistant closure requires that the cap first be rotated to a certain angular position on the container, and then lifted at that position. Another type requires that the cap be pushed toward the container ("palmed") to engage ratchets or threads so that it can be unscrewed. The theory underlying child resistance is that it is conceptually difficult for a small child to appreciate the need to carry out two diverse types of movement simultaneously or sequentially.
However, it is also difficult for some adults to open and/or close some child resistant closures, as for example those in whom arthritis has caused a loss of mobility and dexterity in the fingers. The great majority of child resistant closures require increased force (for example, about two pounds) to open and/or close the cap, but a significant number of adults are unable to exert even this threshold level of force and thus they are effectively prevented from opening such containers. Because of this, some adults deliberately leave a container open to avoid the effort of opening it again; and some actually cannot exert the force necessary to close it once it has been opened. Because typical child resistant closures cannot easily be used by some adults, it has been necessary for suppliers to continue to stock some items in containers with ordinary (non-child resistant) closures, so that a container with either mode of opening can be selected at the time of purchase. There is some evidence that the preference for non-child resistant closures is increasing, which of course increases the risk to children. Thus, there is a need for a closure which will simultaneously or optionally provide the somewhat antithetical requirements of child resistance and selective ease of opening and closing by adults.
Tamper indicating means, another closure safety feature, have a different objective. Their purpose is to provide a clear visual indication that a container has previously been opened which, in the instance of goods on the shelf awaiting purchase, could signify tampering. Usually tamper indication is provided by a band or cover which must be removed, separated, or torn before the closure can be opened, and which thereby gives a visual indication of opening.
However, the operation of tamper indicating means generally tends to slow the opening of a container. In some previous containers which combined tamper indicating with child resistant features, several separate barriers must be sequentially removed before the container can be opened. For example, it is sometimes necessary to tear open a glued carton or remove a shrink band or an inner seal from the top of the container after a child-resistant cap has first been removed. It may be necessary to use an implement such as a knife or scissors to effect the removal. Moreover, once removed, a separable tamper indicating band or wrapper may become litter, or may be chewed or even swallowed by a child. These complicating factors detract from the provision of tamper indicting means.
Yet another problem with some previous containers is that the cap, once removed, is separated from the container and can be misplaced. It cannot be left on or remain attached to the container in a closed but easily openable condition, for ease of use by an adult who does not want child resistance.
Accordingly, there has been a need for a "universal" closure which combines features of (a) child resistance, such that the closure cannot easily be opened by a young child; (b) optional easy opening by adults who might have limited manual strength or dexterity; (c) ease of reclosing; (d) permanent attachment of the closure to the container; (e) absence of littering; and (f) optional automatic tamper indication, to show if the container has previously been opened.